Erectile dysfunction medications seem to improve both the motility and shape of sperm in men who have been diagnosed as infertile. These improvements in sperm quality may make it easier for such men to conceive.
Men with fertility problems might soon find help from an unexpected source, according to a recent Chinese research review. A meta-analysis of data from 11 studies covering more than 1,300 men — many with low sperm counts — found that oral erectile dysfunction drugs, known as PDE5 inhibitors, increased the motility and normalized the shape of sperm these men produced.
Both the motility and shape of sperm are critical factors in any attempt to conceive a child. Motility, a scientific term used primarily in biology, is defined as the ability of fluids and organisms to move around spontaneously and purposefully. These beneficial improvements in sperm quality were seen most often in men who regularly took one of the ED drugs rather than those who used the medications only occasionally.
Only Infertile Men Affected
Interestingly, these improvements in the quality of sperm credited to ED drugs were observed only in men considered infertile due to low sperm counts. Little, if any, changes to sperm quality occurred in men whose sperm counts were considered normal.
Infertility in both men and women is a widespread problem, according to the Eunice Kennedy Shriver National Institute of Child Health and Human Development, or NICHD. Men and women who cannot conceive after a year of regularly having sexual intercourse without birth control are clinically diagnosed as infertile, according to the institute.
The NICHD points out that the inability to conceive can sometimes be traced to a single cause but is often the result of multiple factors. “Overall, one-third of infertility cases are caused by male reproductive issues, one-third by female reproductive issues, and one-third by both male and female reproductive issues or by unknown factors,” according to the NICHD website.
Some Produce No Sperm at All
Roughly 10 to 15 percent of infertile men produce no sperm at all, clearly making it impossible for them to fertilize a female egg and produce a pregnancy, says the NICHD. Male infertility can also be traced to blockages in the male reproductive organs or hormonal imbalances. The precise cause of the problem cannot be determined in an estimated 50 percent of all male infertility cases.
The Chinese research review was conducted by a handful of urology specialists at China’s Sichuan University in Chengdu, capital of the country’s Sichuan province. Their analysis of data from the 11 selected studies found that regular use of PDE5 inhibitors had no effect on sperm volume or sperm concentration. However, they did find increases in the percentage of motile sperm, the percentage of total progressive motility, and rapid progressive motility after the beginning of treatment with oral ED medications.
Sperm Shape, Size Normalized
The Chinese review also found increases in the percentage of normally shaped and sized sperm among infertile men. This led the Chinese scientists to conclude that treatment with oral ED drugs “could modestly increase the sperm motility and morphology in infertile men.” The study’s findings were published in the July 2017 issue of Urology.
As previously noted, these increases in sperm motility and morphology were observed only in men considered infertile because of low sperm count but not in men whose fertility was uncompromised.
How PDE5 Inhibitors Work
The family of ED medications known as PDE5 inhibitors are so called for their ability to temporarily disable an enzyme known as phosphodiesterase-5, which can interfere with optimal blood flow, particularly in men whose vascular systems are already compromised. One of the primary functions of the PDE5 enzyme is to break down a substance known as cyclic guanosine monophosphate, or cGMP, which triggers the smooth muscle tissue lining arteries to relax, thus increasing blood flow.
In an overview of the study’s findings posted at MensHealth.com, writer Christa Sgobba suggested that it’s possible that ED drugs improve sperm quality by enhancing the effects of cGMP, which has been found to play an important role in sperm motility. Backing up Sgobba’s theory is a joint Iranian-Italian study published several years earlier.
Sperm Motility Stimulated
That study, published in the January 2011 issue of Reproduction, found that nitric oxide stimulated sperm motility by activating the pathways for both cGMP and the closely related soluble guanylate cyclase, or sGC.
The results of the Chinese meta-analysis are particularly interesting in light of some earlier studies that suggested that sildenafil, the active ingredient in Viagra, might reduce male fertility. One such study, conducted by researchers at Queen’s University in Northern Ireland, found that sildenafil not only increased the motility of sperm but also caused a premature activation of the acrosome reaction.
The acrosome reaction, common to all placental mammals, including humans, is the process whereby digestive enzymes break down the outer protective layer of the female egg, allowing the sperm to enter and fertilize the egg.
Methodology of Study
David Glenn, a member of the team who conducted the study at Queen’s University, in early 2004 outlined for NewScientist.com the steps taken in the in-vitro study of sildenafil’s effects. Semen samples were collected from 45 men seeking treatment at a fertility clinic in Belfast. Half of the samples were treated with a sildenafil solution calculated to represent the blood levels of Viagra seen in men after they’ve taken a single 100-milligram dose of the drug. The other half of the samples were set aside untreated to serve as a control for the study.
According to Glenn, within 15 minutes the movement of sperm treated with the sildenafil solution showed sharply increased motility, a reaction that continued for 135 minutes on average. Observations taken 120 minutes after the start of the in-vitro study showed that 79 percent more of the sperm treated with sildenafil were fully reacted than the control samples. Researchers also noted that the acrosome reaction occurred earlier in the sildenafil-treated sperm than in the control sample.
Animal Study Cited
The laboratory study’s findings echoed those of an earlier animal study, also conducted at Queen’s University. In that study, male mice were given Viagra and then mated with female mice. The results of those matings were compared with a control group of mice that received no Viagra and were subsequently mated with females. The mice treated with Viagra produced 40 percent fewer embryos than those in the control group. And the embryos produced by the Viagra-treated mice were less likely to survive the five-day blastocyst stage when observed in culture.
Scientists at Queen’s University cautioned that the findings from the animal study would not necessarily be replicated in humans. And based on the Chinese meta-analysis, different results might very well be produced in human sperm that’s been produced by men taking Viagra.
Given the contradictory findings produced by these studies, additional research will be needed to provide definitive evidence, if any, of the pro-fertility properties of oral ED medications.
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